1. Technical Field
The present invention relates to a relay device for relaying transmission of data in an in-vehicle communication system. More specifically, the invention relates to a relay device which can reduce a space occupied by the entire in-vehicle communication system and can easily change the configuration of its system, and also relates to a wiring harness and a communication system that are connected to the relay device.
2. Description of Related Art
In recent years, such a system that includes more than one control devices provided with different functions has been utilized in various fields. The control devices include respective communication means for exchanging data with each other and cooperate together to perform different kinds of processing. Especially in the field of vehicles, the way of controlling is switched from mechanical control to electrical control. A general configuration for the electrical control includes Electronic Control Units (ECUs) provided in a vehicle as a number of control devices, in which the ECUs exchange information with one another via a network in accordance with protocols such as Controller Area Network (CAN), Local Interconnect Network (LIN), FlexRay and the like, and perform various kinds of processing by cooperating and working together.
The number of ECUs mounted in a vehicle is increased because the number of functions implemented by electrical control for the vehicle is also increased. In addition to the system including ECUs mounted in a vehicle, a communication system in which plural control devices work together to perform processing can also distribute segmented processing units to respective control devices. Thus, a problem such as a failure or a bug may easily be isolated and handled in order to enhance efficiency in development and maintenance. Accordingly, the number of control devices included in a communication system as communication equipment is increased, and thus the amount of data transmitted between the control devices in order to cooperate and work together also tends to be increased.
When a communication device is connected to a communication line, a transceiver is used, which realizes transmission of communication signals at a physical layer. The number of transceivers connected to one communication line is limited in order to avoid delay time, reflection and ringing. For example, in the case of CAN which is widely used as an in-vehicle network, though the maximum of thirty transceivers may be connected to a CAN bus conforming High speed according to the standard, the number is, in practice, limited to less than twenty.
Though the number of communication devices included in the communication system tends to be increased, the number of communication devices connected to one communication line is limited. Thus, the communication devices may be divided into groups, each of which is connected to a communication line while a relay device (gateway device) is used for relaying between different communication lines. In such a case, the number of communication lines is increased as the number of communication devices is increased. It is, however, considered to be important, especially in the field of vehicles, to reduce the weight of a vehicle in order to improve fuel consumption and to prevent harmful effects on the environment. To reduce weight, reduction in the weight of a harness itself including various electric wirings such as a power line is most effective. It is thus desired to reduce the weight of various electric wirings and the number of lines in the in-vehicle communication system. Furthermore, there is a limited space available for the installation of the ECU and relay device in order to secure a space as wide as possible in a vehicle and to enhance comfort.
When control devices need to be connected to different communication lines in the communication system, the relay device performs relaying between communication lines. Here, it is wasteful for the control device and relay device to be located separately from each other in different housings and respectively have power supply circuits, clock circuits and the like, when the space for placing them is limited.
Patent Document 1 proposes a connector containing electronic components, which includes electronic components in a connector housing of a harness, can be handled similarly to a general connector and can reduce the size of a housing and a connector for the electronic components.
[Patent Document 1] Japanese Patent Application Laid-Open No. 2008-226809